The present invention relates to thermoplastic molding compositions based on a resinous polyblend to which a polylactone has been added to improve surface gloss, and in particular to aromatic polycarbonate based polyblends to which poly(epsilon-caprolactone) has been added to improve surface gloss.
Aromatic polycarbonates are a widely used class of thermoplastic molding polymers selected for superior molding properties. However, molded aromatic polycarbonate articles lack critical thickness impact strength and chemical resistance. This has been overcome by forming polyblends of polycarbonates with thermoplastic poly(alkylene terephthalates) and elastomeric rubber polymers. Articles molded from such polyblends lack surface gloss, a necessary feature the absence of which makes the polyblends unsuitable for many end use applications.
Polylactones have been shown to be useful property modifiers for resinous thermoplastic molding compositions. U.S. Pat. No. 4,492,782 discloses that polycaprolactone improves the impact strength and dimensional stability of polyester molding compositions. U.S. Pat. No. 4,536,531 discloses that polycaprolactone improves the crystallization rate of polyester molding compositions. U.S. Pat. No. 4,656,206 discloses that polycaprolactone improves the impact strength of polyester molding compositions.
U.S. Pat. No. 4,064,195 discloses that polycaprolactone improves the stress crack resistance of aromatic polycarbonate molding compositions. U.S. Pat. No. 4,388,443 discloses that polylactones compatiblize molding composition blends of aromatic polycarbonate and rubber-modified styrene maleic anhydride.
It has now been discovered that polylactones, when added to a thermoplastic molding composition prepared from a resinous polyblend of an aromatic polycarbonate with a poly(alkylene terephthalate) polyester and an elastomeric rubber improves the surface gloss of articles molded therefrom. The surface gloss of articles molded from the polylactone containing molding compositions is improved without a loss of physical properties important to the end use applications of the articles.